The objective of this research is to study the pathogenesis and reactivation of cytomegalovirus infection, and defense mechanisms against it, using the mouse model. (1) The role of macrophages will be studied beginning with basic virus-macrophage relationships, leading to the role of macrophages in non-specific resistance, and in specific immunity, particularly cellular immunity. (2) Reactivation or accentuation of MCMV infection by graft vs. host and host vs. graft reactions will be studied systematically in infection models using inbred C3H and BALB/C mice and their F1 offspring. (3) The basis of latent and persistent infection in the salivary glands and the kidney will be approached by looking at the structural and cellular peculiarities of these organs. Intact tissues or their cellular derivatives will be transferred to other sites or transplanted to syngeneic animals, and the course of MCMV infection followed.